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Adult ferritin treatment threshold too high for kids with restless sleep

By: DEBRA L. BECK, Family Practice News Digital Network

 JUNE 2, 2014


VITALSKey clinical point: For children with restless sleep, consider iron supplementation at a serum ferritin level of 20 mcg/L.Major finding: A serum ferritin threshold of 20 mcg/L is a better predictor of sleep restlessness in children than is the adult threshold of 50 mcg/L.

Data source: Review of 537 children (1-18 yrs) referred to the University of Michigan pediatric sleep clinic.

Disclosures: The study was supported by a grant from the Charles Woodson Fund for Clinical Research.

 MINNEAPOLIS – Using the adult treatment threshold for serum ferritin to guide treatment in children with restless sleep may lead to inappropriate iron supplementation.

In both adults and children, iron deficiency has been linked to the presence and severity of restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS). For adults, a serum ferritin less than 50 mcg/L is the threshold commonly used to guide iron supplementation for patients with RLS or PLMS. A threshold of 40-50 mcg/L also has been used in pediatric studies.

For children, however, a far lower level of 20 mcg/L appears more appropriate, Alyson Connor and her colleagues reported at the annual meeting of the Associated Professional Sleep Societies.

“Our findings raise a question about the best serum ferritin threshold to use when seeing a child with evidence of sleep restlessness, in particular with elevated” periodic limb movement index, Ms. Connor said, adding a caution that, “while many children may benefit from iron supplementation for these disorders, this area is worthy of further study as investigation in animals suggests that treatment of iron deficiency with high-dose iron supplementation in early development may differentially effect the development of the brain.”

Ms. Connor, a student in the biomedical research program at the University of Michigan, Ann Arbor, and her colleagues conducted a review of 537 children between the ages of 12 months and 18 years who were referred to the University of Michigan pediatric sleep clinic.

In this young cohort (mean age was 8.9 years; 62% were male), a median serum ferritin level of 23.6 mcg/L was associated with polysomnographic measures of periodic limb movement index (PLMI) per hour of total sleep time of 5 or more, while a median level of 30 mcg/L was associated with PLMI less than 5. Overall, about 26% of the subjects had a PLMI of 5 or more.

“There was a significant association between serum ferritin and periodic limb movement index such that, for every 10 mcg/L increase in serum ferritin, it decreased the odds of having an elevated PLMI by 11%, with a P value of .01,” Ms Connor said.

Boys, younger patients, those with lower serum ferritin levels, and those with a shorter time between hematology and polysomnography all had significantly increased odds of a PLMI of 5 or more.

Only 19% of patients studied had a serum ferritin above 50 mcg/L, while 50% had a serum ferritin below 30 mcg/L.

“Essentially, the cutoff of 50 is very sensitive, giving few false negatives, but not very specific, whereas a lower cutoff improves specificity,” Ms. Connor said.

Future studies are needed to assess the association between iron status and sleep measures in a general pediatric population and to determine the best iron dose, timing, and method of delivery for optimal developmental outcomes, she said.

The study was supported by the Charles Woodson Fund for Clinical Research.

Originally posted in Family Practice News

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